AL-PILLARED SAPONITES .2. NMR-STUDIES

A saponite from Ballarat was intercalated with Al polycations by four different procedures involving different sources of polycations, and s tabilised by calcination (pillared). Si-29 and Al-27 solid-state MNR o f both the intercalated and the pillared samples have been measured an d are discussed. Si-29 NMR leads us to propose a pillaring mechanism, involving H+ attack of the clay tetrahedral sheet followed by AlO4 tet rahedra inversion, similar to that previously proposed for beidellites . Al-27 NMR reveals that the pillars are not fundamentally modified up on calcination at 500-degrees-C although they undergo reversible dehyd ration reactions; at 750-degrees-C and above, a strong pillar reorgani sation occurs prior to collapse of the global structure.